1. Field of the Invention
This invention relates to the treatment of refuse, particularly the treatment of refuse for disposal at sea. The invention is applicable to the disposal of refuse generated aboard ship, and also to the disposal of refuse generated on land, such as in municipalities. Various studies have indicated that deep sea disposal of refuse may be accomplished without detrimentally affecting the ocean environment, provided the same can be made to go directly to the bottom of the sea and stay there. A slow degradation of such refuse takes place, and the organic materials can again enter the ecological chain without damage. The difficulty has been to insure that the refuse is delivered promptly to the bottom and that it remains there.
2. Prior Art
The term "refuse" as used herein and as generally understood means any solid wastes other than sewage. Studies have shown that solid wastes collected in typical urban areas comprise approximately 45% paper products, 20% food wastes, 9% metals, 9% glass and ceramics, and 1.5% plastics, with the remainder being principally garden wastes, wood and ashes. Solid wastes generated aboard ship would be expected to be somewhat similar, with perhaps a lower content of metals, no garden wastes or ashes and a high proportion of food wastes. The present method is useful on any mix of solid wastes so long as it includes some quantity of fibrous or porous material which incorporate air in its physical structure. Such materials incorporating air (hereinafter called "porous components") include, for example, wood, paper products and food wastes.
Efforts have been made to dispose of refuse generated aboard ships by compacting it into bales, which are then dumped into the sea. These efforts have been directed largely at achieving higher compaction densities. However, constraints imposed by equipment and energy costs have limited the degree of compaction achievable. As a result, even the highest densities achieved have not proved adequate to reliably insure that the bales go promptly to the bottom. Moreover, such bales must usually be bound with straps or other bindings to hold them together adding materially to the cost of disposal. Even then, particles and larger portions can break free and float on the surface. To avoid such flotsam, partly for security reasons, submarines conventionally carry billets of lead which are inserted in compacted and containerized refuse prior to disposal in order to guarantee that the bale goes promptly to the bottom and stays there.
Apart from shipboard refuse disposal, it has long been recognized that the deep ocean is a viable place to dump municipal wastes if they can be properly prepared and processed so as not to damage the marine or shore environment, see, "Deep Ocean Dumping of Baled Refuse", Sub-Council Report, February, 1971, National Industrial Pollution Control Council, prepared for the United States Department of Commerce. This report recognized that " . . . municipal refuse offers the possibility of packaging into compressed bales which can be deposited in specific selected sites in the deep oceans where biological activity is minimal. Possible pollution hazards in such a disposal system include the floating of components of refuse during the dumping operation or their refloating at a later date, and unacceptable interference with the biological system of the ocean. A properly designed series of experiments could develop acceptable methods for the disposal of municipal refuse in the oceans. The United States, with its pressing municipal refuse disposal problems, should initiate such experiments," p.6. The report advocated baling the refuse to prevent re-floating, i.e. binding it up in bundles which " . . . may have to be securely wrapped in a water penetrable plastic . . . ," p.11. It further recognized that "compacted municipal refuse becomes almost totally impregnated with water and reaches maximum density after a few minutes at a hydrostatic pressure equivalent to a depth of 500-600 feet. Most materials become more dense than water after water impregnation induced by the hydrostatic pressure. These include paper and wood but exclude certain plastics, particularly polyethylene, which make up only 1% to 2% of municipal wastes. This means that baled refuse will sink and, if properly bound together, will stay down. It will not float," p.11. Accordingly, the report recommended a pilot program in which refuse would be " . . . compressed, baled and packaged," and deposited 250 miles at sea. While baled refuse may stay down once exposed to 500-foot depths, however, baling has not been capable of reliably sinking it to that depth; the problem of floating refuse still remains.
Some methods proposed for treating refuse employ binders when compacting, in order to hold the mass together. Proposed as binders for the refuse have been such materials as asphaltum, suggested in U.S. Pat. No. 3,721,183, bitumen, suggested in U.S. Pat. No. 3,654,048, and even water, suggested in U.S. Pat. No. 3,195,447. (Water does not really "bind" the refuse in the sense of bonding it together; the patent apparently refers to the effect of water in allowing the mass to compact more densely.) U.S. Pat. No. 3,934,038 contains a different suggestion, that the refuse be separated into components according to density, and that the components more dense than sea water be sprayed with an organic material as a feed for microorganisms. The spraying is applied both to the shredded refuse and to the compacted bale.
Efforts have also been made to encase the bale to prevent flotsam from breaking away, see for example, U.S. Pat. No. 3,330,088. On the whole, all of these methods have sought to rely upon relatively high pressures to compact the bale to a density sufficient to achieve negative buoyancy, and upon additives to increase weight, cohesiveness and biodegradability, often at material additional cost. Despite these and other efforts at significant cost to achieve a practical method for refuse disposal at sea, it has thus far been impossible, as reflected in published literature, to insure that the entire bale will reliably sink. Despite the fact that almost all refuse is made up of materials which are intrinsically denser (in their chemical makeup) than sea water, the problem of floating bales and particles broken from bales persists.